Document presents suggested revisions to test procedures in Annex 7 and Annex 7 Appendix 1:
Considerations by TF-Data Analysis regarding tyre slopes, power train slopes, and part load model for the RD-ASEP Sound Expectation Model. Tyre slopes α = 40 and β = 20 are confirmed as appropriate for UN R117 approved tyres. Power train slopes are confirmed as well-framed to normal vehicle behaviour and consistent with Annex 7 ASEP Slope-Assessment principles. For part load model, the function is confirmed for ICE vehicles and HEV in ICE mode, while for EVs and HEVs in EV mode the part load area may require reworking, but the part load model should be applied uniformly to all vehicle techniques.
Document presents considerations on amendments to the RD-ASEP Sound Expectation Model SEM. A simplified approach for electric vehicles is proposed based on Supplement 11 to UN R51.03, using a tyre rolling sound curve with slopes identical to internal combustion engine and hybrid electric vehicles, plus an acceleration term from UN R51.03 Supplement 11 as an additional term, and the AVAS term from Option 1, without other parts of the SEM.
Document presents considerations on revising the AVAS term in the RD-ASEP Sound Expectation Model to align with UN R138.02 specifications for electric and hybrid electric vehicles. Two options are discussed: Option 1 implements only constant speed specifications from UN R138.02, while Option 2 extends this with an additional term to reflect interpretation of paragraph 6.2.8 for accelerated conditions. A revised AVAS term formula applicable for vehicle speeds up to 50 km/h is proposed.
Proposal to amend the determination of reference acceleration aREF by introducing a theoretical calculation formula based on PMR, rated engine speed S, and vehicle mass mro, with a correction function accounting for transmission losses, virtual mass increase, tyre slip, and turbo delay, and to allow manufacturers to alternatively determine reference acceleration by discrete measurements.
Document presents considerations on factor x used in the Sound Expectation Model to split constant speed test results into tyre rolling sound and power train mechanic references. Factor x values are concentrated between 80 and 99, indicating tyre dominance. Small variations in measurements cause disproportional variability in the minor sound source when one source dominates. Two options are proposed: Option 1 requires factor x determined during type approval to be reported and used for subsequent assessments, with any redetermination not exceeding the type approval value; Option 2 requires the power train reference from type approval to be used for all further assessments regardless of measurement variations.
Transport Canada presents results from a national survey on vehicle headlight glare conducted from March to April 2026, with 361,438 respondents. Approximately 90% of participants experience glare at least weekly, with oncoming vehicles cited by 97.4% as the primary source. Large SUVs and pickup trucks were identified by 95.4% as causing the most glare. Light intensity, headlight mounting height, and misalignment were the most commonly perceived contributing factors. Survey respondents identified updating headlight design standards (83.6%) and restricting replacement headlight sales (82.8%) as preferred solutions. Transport Canada is conducting ongoing research including a naturalistic driving study and developing a dedicated vehicle headlight glare webpage.
The report of the 4th Session was approved by the delegates.